1. Field of the Invention
The present invention relates to an optical apparatus capable of photographing in a panoramic size. More particularly, the invention relates to an optical apparatus for photographing by switching a Leica size over to a panoramic size.
2. Related Background Art
A panoramic camera is a camera capable of taking a picture of a so-called panoramic size shown in FIG. 19A which is extremely long from side to side as compared with an ordinary picture, and is suited for photographing an extensive scene or the like. The panoramic camera has been in use for a long time. Nevertheless, amateur cameramen in general find it rather difficult to enjoy the panoramic photographing because photographic shops (the so-called labos) are not prepared usually to develop such a film, print it automatically, or perform other processings due to the special frame size of the film.
In recent years, however, a panoramic size film has been developed using a usual 35 mm film (JIS 135), the so-called Leica size of 24.times.36 as shown in FIG. 19B, for example. The panoramic size film, which is now in the spotlight among those who are in the art, is in a size of 13.times.36 mm such as obtainable by narrowing the frame size of the above-mentioned 35 mm film vertically as shown in FIG. 19C. Thus, by maintaining the dimension in the lateral direction the same as the Leica size, it becomes possible to perform the film development and printing with the conventional labo-equipment and instruments. At the same time, the so-called disposable camera dedicated for this type of panoramic film is now available in the market, promoting a rapid popularization thereof among the general amateur cameramen as a panoramic film which they can use without difficulty. In manufacturing a camera, this panoramic film also has an advantage that with the same dimension as the Leica size in the lateral direction, it is possible to implement with ease the camera which can be used both for the usual Leica size and the panoramic size by the use of a shade and others to narrow the exposure area of the film.
In other words, it is possible to implement easily a camera whereby a picture can be taken in the panoramic size by modifying the conventional camera slightly or incorporating some attachment therein. In fact, among camera dilettanti, there are some who modify the conventional 35 mm camera into a panoramic camera by shading the upper and lower parts of the longitudinal direction of the film aperture 10 of the camera body B with think flat shading members 20 as shown in FIG. 20. Recently, a kit for such a modification is commercially available on the market.
With this method, however, while the photographing can be performed in a panoramic size, the angle of view whereby a picture can be taken by a same camera beocmes narrow as compared with the usual state of its use. For example, whereas the photographing lens having its focal length of 35 mm in the Leica size has an angle of view of approximately 63.degree. with the diagonal line contained, the angle of view becomes approximately 57.degree. in the panoramic size, which is equivalent to a focal length of 40 mm in terms of the Leica size. This cannot be termed as a wide angle lens. Also, a lens having a focal length of 28 mm has an angle of view of 63.degree. likewise, but it has an angle of view of only approximately 57.degree. with the diagonal line contained in the panoramic size, which is equivalent to a focal length of 40 mm in terms of the Leica size. With this result, it cannot be said, either, that the angle of view of a wide angle lens has been utilized sufficiently. Also, likewise, a lens having a focal length of 28 mm has an angle of view of approximately 68.degree. with the diagonal line contained in the panoramic size, but it produces a narrow angle of view in the Leica size, which is equivalent to a focal length of 32 mm. As described earlier, the panoramic size is a format which is suited for performing a photographing in a wide area in the lateral direction. It is therefore a considerable disadvantage that the angle of view becomes narrower.
In order to avoid this disadvantage, a photographing lens having an extremely wide angle of view should be prepared in advance. In optical designing, however, the wider the angle of view is, the more difficult it is to design a lens, and it is also unavoidable to increase the manufacturing cost of the camera as a whole and to make the size thereof larger because the numbers of elements to construct a lens increase and the lens diameter becomes greater. Also, when a photographing lens to be installed is a single focus lens, the adoption of a lens having an excessively wide angle of view for the use of the panoramic size photographing may lead to a danger that general users find it difficult to use such a lens because the angle of view becomes wider in taking a picture in the usual Leical size. In addition, it should be mention that a photographing lens is used rather wastefully because with this method the upper and lower part of an objective image are simply shaded for the purpose and the angle of view genuine to such a photographing lens is not fully utilized.